Ball-and-socket joint with bearing shell

ABSTRACT

A ball-and-socket joint includes a joint housing having first and second axial ends and a ball head provided with a ball stud that extends from the ball head. A bearing shell has elastic properties and is received in the joint housing whereby the bearing shell receives the ball head. The ball stud extends outward of the first axial end of the joint housing. The ball-and-socket joint also includes a housing cover for closing the second axial end of the joint housing and a spring element that is interposed between the housing cover and at least a portion of the bearing shell. The spring element preloads the portion of the bearing shell to urge the portion of the bearing shell toward the first axial end of the joint housing thereby plastically deforming the portion of the bearing shell into its final ball-shaped contour.

[0001] The present invention relates to a ball-and-socket jointcomprising a joint housing, a ball head with ball pivot, a bearing shellarranged between ball head and joint housing, and a housing cover.

[0002] Ball-and-socket joints of said type are known in the art and arepreferably used in motor vehicles. The ball head of the ball-and-socketjoint is rotatably and tiltably supported in the bearing shell, and thebearing shell in turn is arranged in the joint housing.

[0003] The purpose of the bearing shell, which is usually exposed tohard wear, is to compensate the lateral forces acting on theball-and-socket joint and to absorb shocks to the joint housing and tothe ball pivot. The bearing shell is therefore advantageously made of anelastic plastic that can be elastically deformed as a result of theforces acting on the ball-and-socket joint.

[0004] To ensure that the ball head is not enclosed too tightly by thebearing shell during assembly of a ball-and-socket joint of theinitially mentioned type and that the joint is not too stiff, tightmanufacturing tolerances are required particularly in the production ofthe joint housing. To compensate stiffness of the ball-and-socket jointdue to imprecise manufacturing tolerances, a bearing shell has beenproposed, which at one end face is provided with very small projectionswhose height slightly exceeds the manufacturing tolerances of the joint.These projections are deformed when correspondingly high forces areapplied as the joint is assembled and have the purpose of compensatingthe manufacturing tolerances of the joint members such that thetolerance for free movement of the ball-and-socket joints can be keptwithin limits. However, wear of the bearing shell cannot be compensatedby these projections.

[0005] With increasing wear of the bearing shell, an undesirable,continuously increasing bearing clearance develops between ball head andbearing shell. With respect to the operating life of the ball-and-socketjoint this causes a change in the motive torques of the bearing journalas well as a continuous change in the elasticity properties of thebearing shell. As a consequence, the bearing is no longer exact, whichresults in imprecise wheel guidance of the ball-and-socket joint andnoise development.

[0006] Thus, based on this prior art, the object of the presentinvention is to further develop a ball-and-socket joint of the initiallymentioned type to reduce the tolerance of free movement and increase thelife of the ball-and-socket joint while simultaneously simplifying theassembly.

[0007] To attain this object, it is proposed according to the inventionthat a compressive force, which is produced between the housing coverand at least a portion of the bearing shell and axially acts in thedirection of the ball pivot, permanently acts on this portion of thebearing shell and presses it into the gap between ball head and jointhousing.

[0008] This ball-and-socket joint designed according to this technicalteaching advantageously allows the compensation of inaccuracies that aredue to manufacturing tolerances of the joint members as well to wear.Unlike in prior art processes, the ball-and-socket joint according tothe invention is assembled with an intentional axial clearance of thebearing shell in relation to the rolled-in housing cover with respect toboth maximum and minimum manufacturing tolerances. The compressiveforce, which on the cover-side permanently acts in axial direction ofthe ball pivot on at least a portion of the bearing shell, presses thisportion of the bearing shell into the gap between ball head andball-and-socket joint such that, independent of the differentmanufacturing tolerances of the individual ball-and-socket jointcomponents, the ball head is supported in the bearing shell under theaction of axial forces that are always the same so that differentfreedoms of movement of the ball joints are avoided. The compressiveforce can be applied to the bearing shell either directly below thehousing cover or it can act on any intersection line or plane as a partof the bearing shell. Due to tolerance compensation, the motive torquesof the ball-and-socket joint and the elastic properties of the bearingshell are thus largely independent of the manufacturing process and theresultant manufacturing tolerances of the joint members. Furthermore,the tilting torque of the ball-and-socket joint and the elasticities ofthe bearing shell can be adjusted in an advantageous manner bycorrespondingly selecting the compressive force acting on the bearingshell after assembly of the ball-and-socket joint. This makes itpossible to produce ball-and-socket joints with low motive torques andelasticities while keeping dimensional tolerances acceptable in terms ofprocess engineering with less variation of the joint properties.

[0009] The ball-and-socket joint according to the invention alsoadvantageously compensates wear of the bearing shell. The compressiveforce permanently acting on the bearing shell causes the bearing shellto advance continuously as wear occurs, such that, in terms of a “selfadjustment” of the bearing shell, the ball head is always supported inthe bearing shell under the action of identical axial-elastic wedgeeffects. This ensures largely constant motive torques of theball-and-socket joint on the one hand and essentially unchanging elasticproperties of the bearing shell on the other hand, which advantageouslyincreases the life of the ball-and-socket joint.

[0010] To produce the compressive force permanently acting on thebearing shell, the present invention proposes plastically to deform thehousing cover in axial direction of the ball pivot with a specificallydefinable force. A disk made of an elastic material and disposed betweenhousing cover and bearing shell is elastically deformed by the plasticdeformation of the housing cover. This generates a preloading force thatis applied to the bearing shell as a permanently acting compressiveforce. Thus, a defined pressing in of the housing cover makes itpossible to achieve an exactly definable preloading force of theball-and-socket joint. According to a particular advantage of theinvention, both the housing cover and the disk have an outwardly facingtrapezoidal curvature. The inside [ . . . ] and of the housing cover[sic] rests against and fully contacts the disk in the area of thetrapezoidal curvature based on a defined applied force and a deformationof the housing cover. This effect can furthermore be enhanced in thatthe torque of the ball pivot is measured or monitored as the housingcover is pressed in, and the measured data is used to control thepressing-in force.

[0011] According to an alternative embodiment, the compressive forcepermanently acting on the bearing shell is produced by means of a springthat is arranged between the housing cover and the bearing shell andsupported against the joint housing via the housing cover. Withparticular advantage, it is proposed that the spring is a trapezoidaldisk spring with an outward curvature. When the joint housing is closedwith a rigid housing cover, the disk spring disposed between bearingshell and housing cover is compressed and the resultant spring forcepermanently acts on the bearing shell in axial direction of the pivotpin in the form of a compressive force. By selecting a correspondingdisk spring and its initial stress, the disk spring force and thus alsothe preloading force of the ball-and-socket joint can be adjusted.According to a further advantageous proposal of the invention, anadditional load transmission disk may be disposed between disk springand bearing shell to optimize introduction of the force into the bearingshell. In a further advantageous embodiment, the contact area betweenspring and disk is designed as a deformable area. During assembly, afterflattening of the spring, this area is deformed to a sufficient degreeuntil the bearing shell has reached its axial end position. The initialpreloading of the joint is thus independent of the tolerances of theindividual components and the size of the spring force.

[0012] According to an alternative embodiment, the bearing shellarranged between ball head and joint housing has a two-part design andis divided into an upper shell and a lower shell. This partitioning ofthe bearing shell into two parts advantageously creates two mutuallyindependent functional areas that may be designed according to therequirements they are intended to meet. For example, the upper shellserves to compensate the inaccuracies due to the manufacturingtolerances of the joint members, whereas the lower shell compensateswear.

[0013] To compensate the inaccuracies due to the manufacturingtolerances in the assembly of the ball joint, the invention proposesthat the upper shell, on the housing cover side, be provided with acollar, which in the assembled state of the ball-and-socket joint iswedged between the housing cover and a housing shoulder. To assemble theball-and-socket joint, a compressive force acting in axial direction ofthe ball pivot is generated on the cover side and applied via thehousing cover to press the bearing shells into the gap between ball headand housing. The compressive force acting during assembly is transmittedfrom the upper shell to the lower shell. The inaccuracies due to themanufacturing tolerances of the joint members can be compensated due toa plastic deformation of the collar arranged between the actual uppershell and the housing cover. The axial end position of the upper andlower shell is established as a function of the tolerances of theindividual components, such that, irrespective of manufacturingtolerances, the ball head is supported in the bearing shell anddifferent freedoms of movement of the ball-and-socket joints areavoided.

[0014] According to a further feature of the invention, to compensatewear of the bearing shell, a spring element is disposed in axialdirection between upper shell and lower shell. In the assembled state,this spring element is supported against the housing cover via the uppershell and produces a compressive force permanently acting on the lowershell, which causes a continuous advancement of the lower shell as wearoccurs. This allows a “self-adjustment” of the lower shell of the ballhead under the action of axial-elastic wedge effects that remain alwaysthe same and achieves, on the one hand, motive torques that are largelyconstant and on the other hand essentially unchanged elastic propertiesof the bearing shell. This advantageously prolongs the life of theball-and-socket joint. According to a further feature of the invention,the spring element disposed between upper shell and lower shell is aspring washer of a wave-shaped design that is pushed up completely afterassembly and thus can transmit the full magnitude of the assemblycompressive force to the lower shell.

[0015] Insertion of the bearing shell into the joint housing can becarried out in separate consecutive steps, or the individual components,lower shell, spring element and upper shell, can be combined into apacket and inserted into the joint housing as a unit in a singleassembly step. To form the assembly packet, the upper and lower shellcan be fabricated in a common injection mold with a corresponding recessbeing provided to receive the spring element that separates the lowershell from the upper shell. Irrespective of whether the bearing shell isassembled in a single step or in multiple steps, it has proven to beadvantageous to give the lower shell a cylindrical contour prior to itsassembly and in contrast to its embodiment after completed assembly.

[0016] Further details and advantages of the invention will become clearfrom the following description by means of the drawings in which

[0017]FIG. 1 is a sectional view of a ball-and-socket joint with anintegrally formed housing cover,

[0018]FIG. 2 is a sectional view of a ball-and-socket joint with a diskspring disposed between bearing shell and housing cover according to afirst embodiment,

[0019]FIG. 3 is a sectional view of a ball-and-socket joint with a diskspring disposed between bearing shell and housing cover according to asecond embodiment,

[0020]FIG. 4 is a sectional view of a ball-and-socket joint with atwo-part bearing shell and a spring washer,

[0021]FIG. 5 is a three-dimensional view of the spring washer accordingto FIG. 4.

[0022] The ball-and-socket joint depicted in FIG. 1 essentiallycomprises a ball head 2 with integrally formed ball pivot 3 and a jointhousing 1 sealed with a housing cover 5. The ball head 2 is supported ina bearing shell 4, which in turn is arranged in joint housing 1. Thebearing shell 4 is designed as one piece, contacts the ball head 2 withits sliding surface 7 on both sides of the equatorial plane 8 andsupports it.

[0023] As the ball-and-socket joint is assembled, a precisely definedforce F_(v) is applied to the housing cover 5 provided with an outwardlyfacing trapezoidal curvature, which causes a plastic deformation of thehousing cover 5 in the area of the trapezoidal curvature. In thisfigure, force F_(v) is indicated by a dashed line. Based on this plasticdeformation of the housing cover 5, the disk 6 disposed between bearingshell 4 and housing cover 5 is elastically deformed and applies apermanent compressive force to the bearing shell 4 in axial direction ofthe ball pivot 3. This causes bearing shell 4 to be pressed into the gapbetween joint housing 1 and ball head 2. This has the advantage that theball-and-socket joint is not susceptible to manufacturing tolerances ofthe joint members, particularly of joint housing 1 and ball head 2, andthat the preloading force of the ball-and-socket joint can be adjustedby means of the precisely defined pressing-in force F_(v). The motivetorques of the ball-and-socket joint, which are determined by thepreloading force as well as the elastic properties of the bearing shell4 can thus also be specifically adjusted via the pressing-in force F_(v)irrespective of the manufacturing tolerances. This makes it possible toproduce a ball-and-socket joint with low motive torques andelasticities, which despite acceptable dimensional tolerances in termsof process engineering has a narrow variation range with respect to themotive torques and the elasticities. As wear occurs in the bearing shell4, the compressive force permanently acting on the bearing shell causesthe bearing shell 4 to advance into the gap between ball head 2 andjoint housing 1. This “self-adjustment” of the bearing shell 4 ensuresnearly identical motive torques and elasticity properties despite wear.Prior to assembly, the bearing shell preferably has a cylindricalcontour 23 on the pivot side, which only after assembly is plasticallydeformed into its final ball-shaped contour.

[0024] In the embodiment of the ball-and-socket joint according to theinvention shown in FIG. 2, the compressive force permanently acting onthe bearing shell 4 in axial direction of the ball pivot 3 is producedby means of a disk spring 9 disposed between bearing shell. 4 andhousing cover 5. For better force application to the bearing shell 4, aload transmission disk 6 is arranged between disk spring 9 and bearingshell 4. The desired preloading force of the ball-and-socket joint canbe adjusted through a corresponding selection of the disk springproperties. As described above, the compressive force generated by thedisk spring 9 and transmitted to the bearing shell 4 also serves topress the bearing shell 4 into the gap between the ball head 2 and jointhousing 1. Consequently, the ball-and-socket joint is not susceptible tomanufacturing tolerances on the one hand, and the wear contour 10 iscompensated by an axial advance of the bearing shell on the other hand.The embodiment of the joint housing 1 shown in FIG. 2 has asubstantially cylindrical inner contour starting from the equatorialplane 8 of the ball head 2 toward the cover-side end. This innercontour, according to a special embodiment of joint housing 1, can beconical with a tapering diameter in the direction of the equatorialplane 8 of the ball head 2. This is indicated by the dashed line 11. Ifa joint housing 1 with conical inner contour is used, the bearing shell4 is correspondingly adapted. The conical embodiment of the innercontour advantageously reduces the torque of the ball-and-socket jointcaused by the permanently acting compressive force of the spring 9.According to a further embodiment of the ball-and-socket joint, anelastic ring made of rubber is disposed between bearing shell 4 andhousing cover 5 instead of the disk spring 9.

[0025] In a further preferred embodiment, the contact area betweenspring 9 or disk 6 is made as a deformable area 24. During assembly,this area, after flattening of the spring, is deformed to a sufficientdegree until the bearing shell 4 has reached its axial end position. Theinitial preloading of the joint is thus independent of the tolerances ofthe individual components and the size of the spring force.

[0026]FIG. 3, according to a second embodiment, also shows aball-and-socket joint with a spring disk 9 disposed between bearingshell 4 and housing cover 5. In contrast to the embodiment depicted inFIG. 2, a circumferential collar 17 is provided instead of a loadtransmission disk disposed between disk spring 9 and bearing shell 4. Inthe assembled state of the ball-and-socket joint this collar 17 restsagainst the disk spring 9 and transmits the compressive force generatedby the disk spring 9 to the bearing shell. The circumferential collar 17and the bearing shell are designed as one piece, but in contrast to theembodiment shown in FIG. 2, the bearing shell is formed as a closedbearing shell 12. The collar 17 is provided with a shoulder 18 and withsnap locking means 19 for a secure seat of the disk spring 9. Asexplained above in connection with the embodiment according to FIG. 2,the desired preloading force of the ball-and-socket joint can beadjusted via a corresponding selection of the disk spring properties inthis embodiment as well.

[0027]FIG. 4 shows an embodiment of the ball-and-socket joint accordingto the invention with a two-part design of the bearing shell comprisingan upper and a lower shell 13, 14, and 15. The embodiment depicted onthe left of the drawing shows an upper shell 15 with an open design andthe embodiment depicted on the right half of the figure shows an uppershell 14 with a closed design. The upper shell 14, 15 has an integrallyformed circumferential collar 17 on the cover side, which in theassembled state of the ball-and-socket joint is wedged between thehousing cover 5 and the housing shoulder 20. This circumferential collar17 has deformable areas 21 and 22 that have a tolerance compensatingeffect on the axial position of the upper and lower shell 14, 15, 16when the joint is assembled. To compensate wear of the bearing shell, aspring element in the form of a wave-shaped washer 16, is providedbetween the upper shell 14, 15 and the lower shell 13. This springwasher 16 is supported against the housing cover 5 via the upper shell14,.15 and applies a compressive force permanently acting on the lowershell 13, which causes the lower shell 13 continuously to advance aswear occurs. This “self adjustment” of the lower shell 13 makes itpossible that the ball head 2 is supported in the bearing shell 12 underthe action of axial-elastic wedge effects that remain always the same.During assembly, this spring washer is flattened and the full magnitudeof the assembly compressive force is thereby transmitted from the upperto the lower shell.

[0028] In contrast to the embodiments depicted in FIG. 1 to 3, thetwo-part embodiment of bearing shell 12 has the effect of a functionaldivision. The upper shell 14, 15 with its integrally formed rim 17serves to compensate inaccuracies due to manufacturing tolerances,whereas the lower shell 13 compensates wear. With this function-relateddivision between upper and lower shell 13, 14, 15 and the arrangement ofa spring washer 16 between upper and lower shell 13, 14, 15, the springforce required for the advancement of the shell is advantageouslyreduced substantially so that low motive torques can be realized.

[0029]FIG. 5 is a three-dimensional representation of the wave-shapedspring washer 16 between upper and lower shell 13, 14, 15 in itsnon-stressed state. Under the action of the pressing-in force that isapplied to the bearing shell during assembly, ring 16 is compressed andthereafter tries to expand in axial direction to assume the non-stressedstate depicted in FIG. 5. Due to this expansion tendency of the springwasher 16, the lower shell 13 is pressed into the gap between ball head2 and joint housing 1, which makes it possible to compensate wear ofbearing shell 12.

[0030] List of Reference Symbols

[0031]1 ball-and-socket joint

[0032]2 ball head

[0033]3 ball pivot

[0034]4 bearing shell

[0035]5 housing cover

[0036]6 disk

[0037]7 sliding surface

[0038]8 equatorial plane

[0039]9 spring

[0040]10 wear contour

[0041]11 dashed line

[0042]12 closed bearing shell

[0043]13 lower shell

[0044]14 closed upper shell

[0045]15 open upper shell

[0046]16 spring washer

[0047]17 collar

[0048]18 shoulder

[0049]19 snap locking means

[0050]20 shoulder

[0051]21 deformable area

[0052]22 deformable area

[0053]23 cylinder-shaped contour

[0054]24 deformable area Page 3

1-16. (Cancelled)
 17. A ball-and-socket joint comprising: a jointhousing having first and second axial ends; a ball head provided with aball stud extending from the ball head; a bearing shell having elasticproperties and being received in the joint housing whereby receiving theball head, the ball stud extending outward of the first axial end of thejoint housing; a housing cover for closing the second axial end of thejoint housing; and a spring element interposed between the housing coverand at least a portion of the bearing shell preloading the portion ofthe bearing shell to urge the portion of the bearing shell toward thefirst axial end of the joint housing thereby plastically deforming theportion of the bearing shell into its final ball-shaped contour.
 18. Theball-and-socket joint as claimed in claim 17 wherein the spring elementadvances the portion of the bearing shell toward the first axial end ofthe joint housing for wedging the portion of the bearing shell furtherinto a gap formed between the ball head and the joint housing adjacentthe ball stud at the first axial end of the joint housing as wear to theportion of the bearing shell occurs.
 19. The ball-and-socket joint asclaimed in claim 17 wherein the spring element is a disk that isarranged between the housing cover and the bearing shell, wherein centerportions of both the housing cover and the disk extend outwardly awayfrom the ball stud.
 20. The ball-and-socket joint as claimed in claim 19wherein the housing cover is made of a plastically deformable material,the center portion of the housing cover being axially deformable towardthe ball stud.
 21. The ball-and-socket joint as claimed in claim 20wherein the center portion of the housing cover contacts the centerportion of the disk to urge the disk against the bearing shell.
 22. Theball-and-socket joint as claimed in claim 17 wherein the bearing shellincludes a deformable area, the deformable area enabling the bearingshell to be adapted for use with joint housings of varying tolerances.23. The ball-and-socket joint as claimed in claim 17 wherein the bearingshell includes separate and distinct first and second parts, the firstpart being an upper shell and,the second part being a lower shell. 24.The ball-and-socket joint as claimed in claim 23 wherein the springelement is arranged between the upper shell and the lower shell, thelower shell being the portion of the bearing shell that is plasticallydeformed.
 25. The ball-and-socket joint as claimed in claim 24 whereinthe spring element is a wave-shaped spring washer.
 26. A ball-and-socketjoint comprising: a joint housing having first and second axial ends; aball head provided with a ball stud extending from the ball head; abearing shell receivable in the joint housing for supporting the ballhead in the joint housing for pivotal movement relative to the jointhousing, the bearing shell supporting the ball head so that the ballstud extends out of the first axial end of the joint housing; a housingcover for closing the second axial end of the joint housing; and aspring element interposed between the housing cover and at least aportion of the bearing shell, the spring element urging the portion ofthe bearing shell toward the first axial end of the joint housing and,as wear to the portion of the bearing shell occurs, wedging the portionof the bearing shell into a gap formed between the ball head and thejoint,housing adjacent the first axial end of the joint housing so as tocompensate for the wear, the portion of the bearing shell, prior tobeing assembled into the joint housing, having a cylindrical contourand, upon being assembled into the joint housing and being subjected toa preloading force, plastically deforming into a ball-shaped contour.